Plunger construction for free piston pump for well casing



D. G. KNOX May 7, 1957 PLUNGER CONSTRUCTION FOR FREE PISTON PUMP FOR WELL CASING Filed June 11, 1954 3 Sheets-Sheet l w M W N m 6 m I W A "1 5 W W k k\ (I.' i! x x E m I i it I! -i wmwi I IiMH: w M 1 v 0 B w 3 m J 4 5 5 M" 5 o M /I 5 1 f I TVW m I W Z 5 w w 3% 5 .5

D. G. KNOX May 7, 1957 PLUNGER CONSTRUCTION FOR FREE PISTON PUMP FOR WELL CASING Filed June 11, 1954 3 Sheets-Sheet 2 00A/420 6'. ale/0X,

INVEN TOR rivex/ffls' D. G. KNOX 2,791,181

PLUNGER CONSTRUCTION FOR FREE PISTON PUMP FOR WELL CASING May 7, 1957 3 Sheets-Sheet 3 Filed June 11, 1954 m a mm w 0 g j W 0 0 PLUNGER CONSTRUCTION FOR FREE PISTON P FOR WELL CASING Donald G. Knox, Rolling Hills, Calif., assignor to The National Supply Company, Pittsburgh, Pa, :1 corporation of Pennsylvania Application June 11, 1954, Serial No. 436,111

6 Claims. (Cl. 103-52) This invention relates to free piston pumping apparatus of the type employed for raising oil from wells.

Free piston pumping apparatus has been commercially employed for many years. In conventional installations, a plunger travels the entire distance from the producing zone to the well head and return. In such installations, the plunger travels in a string of tubing which extends from the well head to the production zone in the well. The plunger has an axial opening therethrough and a valve for closing the opening. When the plunger is raising a slug of oil, the 'valve is closed so that the plungerand its load of oil may be raised to the surface by means of gas pressure in the tubing below the plunger. When the plunger reaches the well head, the Valve is opened mechanically or by pressure differential, thereby allowing the plunger to drop back down through the tubing by gravity. The plunger drops through the column of well fluid which has accumulated in the lower end of the tubing. The downward motion of the plunger is arrested by a foot piece in the tubing and the parts are arranged so that contact with the foot piece serves to close the valve in the plunger. When sumcient gas pressure is applied I under the plunger, it again raises a load of well fluid to the surface and the cycle repeats.

It is common practice to supplement the gas produced by the well by injecting gas under pressure into the upper ends of the well casing. This gas pressurizes the annulus between the casing and the tubing and enters the tubing at a location below the foot piece.

In certain wells which produce large quantities of gas, it is unnecessary to add additional gas into the casing at the well head. Furthermore, in wells of this type which are capable of large volume production of well fluid, the relatively small size of the tubing makes it difficult to obtain maximum production from the well. it is the principal object of this invention to provide a free piston pumping system in which the plunger operates directly in the casing and without any tubing in the well.

Other and more detailed objects and advantages will appear hereinafter.

In the drawings:

Figure 1A is a sectional side elevation showing a well head equipped for free piston pumping; through the casing.

Figure 1B is a sectional side elevation showing the foot piece removably mounted within the casing.

Figure 2 is a sectional elevation of a portion of the plunger showing details of construction, the plunger valve being in open position.

Figure 3 is a view similar to Figure 2 showing the plunger valve in closed position.

Figures 4, 5, 6 and 7 are transverse sectional elevations taken substantially on the lines 4-4, 5-5, 6-6 and 77, respectively, as shown in Figure 2.

Figure 8 is a perspective view showing the back side of one of the depression bars.

Figure 9 is a perspective view showing the front side of one of the depression bars.

Accordingly,

2,791,181 Patented May 7,1957

Figure 10 is a perspective view showing one of the ring segments.

Referring to the drawings, the well head assembly generally designated 10 includes a housing mounted on the upper end of .a short length of pipe 12. This pipe 12 is, in turn, ailixed to a gate valve generally designated 13. The casing 14 extends downward from the valve 13 into the well bore. The plunger generally designated 15 is adapted to travel within the casing 14 to the upper limit of its travel, as shown in Figure 1A.

' A foot piece generally designated 16 is mounted within the lower portion of the casing 14 near the production zone and serves as a bumper stop to limit downward movement of the plunger 15. This footpiece may include a tapered body 17 fixed Within the casing by means of a set of wedge slips 18. The coil spring 19 serves to maintain the slips 18 in gripping position. The foot piece 16 has a central bore 20 which extends axially there-' through. A bumper spring 21 supports an annular contact piece 22 which is provided with an upwardly facing abutment surface 23.

The central axial opening through the foot piece 16 is necessary in order to enable the foot piece to be lowered into the casing and set at the desired elevation by means of conventional tools not shown. Such tools include a mandrel member which extends axially through the opening 20.

A bumperspring '24 is'mounted within the housing 11 at the well head and acts against a bumper plate 25. The plunger 15 strikes this bumper plate to limit its upward movement. As best shown in Figures 2 and 3, the

plunger 15 includes abody 26 havinga central axial opening 27. The body isgenerally cylindrical on its upper surface 28 and is provided with two sets of axially extending slots 2? in the outer surface thereof. The two sets of slots are not in alignment. As shown in the drawings, each set includes four slots and two sets are, therefore, angularly misaligned by Ms revolution. The slots 29 have parallel sides and each slot receives a depression bar 30 which is mounted to move radially with respect to its respective slot. An axially extending'tab 31 on each end of each depression bar 30 underlies a stationary shoulder 32 to limit radial movement of the depression bar in an outward direction.

A series of ring segments 33 cooperate with the depression bars 30 to provide a substantially continuous surface for sealing against the inside of the casing 14. Springs 34 are provided for urging the segments 33 radially out wardly. A fin 35 on the back face of each depression bar extends between adjacent ends of the ring segments 33. The ring segments are slidably received within circumferential grooves 36 provided on the body 26. The circular grooves intersect the axial slots 29, as shown in Figure 4. The arrangement of ring segments and'depression bars is similar to that shown and described in the Knox et al. Patent 2,642,002issued June 16, 1953.

The lower portion of the body 26 may be formed as a separate extension piece 37 and this extension piece serves to clamp in position a ring member 38 having'a plurality of spring fingers 39 mounted thereon. These fingers are 1 adapted to engage the outer surface of the valve stem 40.

This valve stem is. slidably received in a ported guide 27 which extends, through the interior of the plunger. I

When the valve is in closed position, as shown in Figure 3, communication between the interior of the plunger and the space below the plungeris cut off.

As shown in Figure 3, the spring fingers 39 are sufficiently resilient to enable them to grip the relatively large cylindrical surface 48 on the stem 40 as well as to grip the smaller diameter cylindrical surface 49. The friction resistance developed between the spring fingers and the surface 48 serves to maintain the valve head 43 in closed position against the seat surface 45.

When the plunger 15 is moving upward in the casing 14 under the force of gas pressure exerted below it, the valve is closed as shown in Figure 3 and the spring fingers 39 frictionally engage the stem 40 to assist in maintaining the valve in closed position. When the plunger 15 enters the well head, the stationary spear 50 which is fixed on the bumper plate 25 projects downward into the central opening 27. The lower end 51 of this spear is engaged by the upper end 52 on the valve stem 48, thereby moving the valve to open position as shown in Figure 2. This mechanical opening of the plunger valve is shown in my copending application, Serial No. 106,579 filed July 25, 1949, now Patent No. 2,699,121 granted January 11, 1955. A pivoted trigger element 53 is engaged by the outer surface of the plunger 15 and caused to operate a mechanism 54 which serves to control the action of a valve (not shown) in the flow line leading from the well. This flow line may be connected to one or both of the ports 55 in the housing 11. The action of this mechanism 54 is described in the copending application of John D. Spalding, Serial No. 349,513 filed April 17, 1953, and entitled Free Piston Well Pump, now Patent No. 2,757,614 granted August 7, 1956.

When the plunger valve opens, the plunger drops by gravity down through the casing and through the well fluid which is collected within the casing. The abutment surface 56 on the lower side of the valve head 43 strikes the corresponding abutment surface 23 on the springmounted contact piece 22. The impact developed by engagement of the abutment surfaces 56 and 23 is suflicient to close the valve against the action of the spring fingers 39 in riding over the tapered shoulder 57 between the cylindrical surfaces 48 and 49. Gas pressure within the casing and below the plunger 15 then causes the plunger to raise another slug of well fluid to the surface through the casing 14.

Although the couplings connecting the casing sections are not shown in the drawings, it will be understood that the expansible elements 30 and 33 on the plunger 15 maintain an effective seal between the plunger and the casing even when the plunger is passing through one of the coupling connections. The length of the depression bars 30, together with the bowed shape of the outer surface thereof, prevents hanging-up" or interference between the segment rings 33 and any shoulders at the joints between casing sections.

Having fully described my invention, it is to be understood that I do not wish to be limited to "the details set forth, but my invention is of the full scope of the ap pended claims.

I claim:

1. A fluid-operated swab plunger for travel in a sectional well casing having a footpiecetherein, comprising in combination: a body having a central opening extending therethrough, radially expansible, sealing means on the body adapted to form sealing contact with the interior of the well casing, a downwardly-facing valve seat at the lower end of the body, a valve stem mounted for movement axially of the body and positioned in the lower portion thereof, guide means in the body above said seat slidably engaging the valve stem, a valve head on the lower end of said stem and positioned below said seat, the valve head having an upwardly-facing surface engageable with the valve seat to prevent flow of fluid through said central opening, friction means within the It body engaging the valve stem to maintain the valve head surface remote from said seat to permit flow of fluid through the central opening, the valve head also having a downwardly facing abutment adapted to engage the said footpiece to close the valve head against said valve seat and to arrest downward movement of said body.

2. A fluid-operated swab plunger for travel in a sectional well casing having a footpiece therein, comprising in combination: a body having a central opening extending therethrough, radially expansible sealing means on the body adapted to form sealing contact with the interior of the well casing, a downwardly-facing valve seat at the lower end of the body, a valve stem mounted for movement axially of the body and positioned in the lower portion thereof, guide means in the body above said seat slidably engaging the valve stem, a valve head on the extreme lower end of said stem and positioned below said seat, the valve head having an upwardly-facing surface engageable with the valve seat to prevent the flow of fluid through said central opening, a plurality of axially extending spring fingers within the body frictionally engaging the outer surface of the valve stem to resist axial movement thereof, the valve head also having a downwardly facing abutment adapted to engage the said footpiece to close the valve head against said valve seat and to arrest downward movement of said body.

3. A fluid-operated swab plunger for travel in a sec tional well casing having a footpiece therein, comprising in combination: a body having a central opening extending therethrough, radially expansible sealing means on the body adapted to. form sealing contact with the interior of the well casing, a downwardly-facing valve seat at the lower end of the body, a movable valve element including a valve stem mounted for movement axially of the body and positioned in the lower portion thereof, guide means in the body above said seat slidably engaging the valve stem, said valve element also including a valve head on the lower end of said stem and positioned below said seat, the valve head having an upwardly-facing surface, said valve element being movable upwardly from an open position permitting flow of fluid through said central opening to a closed position in which said upwardlyfacing surface engages said downwardlyfacing valve seat to prevent the flow of fluid through said central opening, means within the body engaging the outer surface of the valve stem acting to releasably maintain the valve element in open position, the valve head also having a downwardly facing abutment adapted to engage the said footpiece to close the valve head against said valve seat and to arrest downward movement of said body.

4. A fluid-operated swab plunger for travel in a sectional well casing having a footpiece therein, comprising in combination: a body having a central opening extending therethrough, radially expansible sealing means on the body adapted to form sealing contact with the intenor of the well casing, a downwardly facing valve seat at the lower end of the body, a movable valve element including a valve stem mounted for movement axially of the body and positioned in the lower portion thereof, guide means in the body above said seat slidably engaging the valve stem, said valve element also including a valve head on the lower end of said stem and positioned below said seat, the valve head having an upwardly-facing surface, said valve element being movable upwardly from an open position permitting flow of fluid through said central opening to a closed position in which said upwardly-facing surface engages said downwardly-facing valve seat to prevent the flow of fluid through said central opening, a plurality of axially extending spring fingers within the body engaging the outer surface of the valve stem to releasably maintain the valve element in either open or closed position, the valve head also having a downwardly facing abutment adapted to engage the said footpiece to close the valve head against said valve seat and to arrest downward movement of said body.

5. In a free piston pumping installation, the combination of: a well casing, a fluid-operated swab plunger for travel within the casing, said plunger having a body pro vided with a central opening extending therethrough, radially expansible sealing means on the body adapted to form sealing contact with the interior of the well casing, a downwardly-facing valve seat at the lower end of the body, a movable valve element including a valve stem mounted for movement axially of the body and positioned in the lower portion thereof, guide means in the body above said seat slidably engaging the valve stem, said valve element also including a valve head on the lower end of said stem and positioned below said seat, the valve head having an upwardly-facing surface, said valve element being movable upwardly from an open position permitting flow of fluid through said central opening to a closed position in which said upwardly-facing surface engages said downwardly-facing valve seat to prevent the flow of fluid through said central opening, a spear mounted at the upper end of the casing adapted to enter the central opening to engage the upper end of the valve stem to open the valve, and a bumper element in the casing at the lower end of the travel of the plunger adapted to contact the valve head to close the valve, and arrest downward movement of the plunger.

6. In a free piston pumping installation, the combination of: a Well casing, a fluid operated swab plunger for travel within the casing said plunger having "a body provided with a central opening extending therethrough,

radially expansible sealing means on the body adapted 30 to form sealing contact with the interior of the well casing, a downwardly-facing valve seat at the lower end of the body, a movable valve element including a valve stem mounted for movement axially of the body and positioned in the lower portion thereof, guide means in the body above said seat slidably engaging the valve stem, said valve element also including a valve head on the lower end of said stem and positioned below said seat, the valve head having an upwardly-facing surface, said valve element being movable upwardly from an open position permitting flow of fluid through said central opening to a closed position in which said upwardly-facing surface engages said downwardly-facing valve seat to prevent the flow of fluid through said central opening, means within the body engaging the outer surface of the valve stem acting to releasably maintain the valve element in either open or closed position, a spear mounted at the upper end of the casing adapted to enter the central opening to engage the upper end of the valve stem to open the valve, and a bumper element in the casing at the lower end of the travel of the plunger adapted to contact the valve head to close the valve, and arrest downward movement of the plunger.

Claytor Sept. 30, 1930 Eddins Dec. 30, 1941 

